JPH08225317A - Amorphous sodium silicate-metal sulfate composite powder and its production - Google Patents

Abstract

PURPOSE: To provide a powder composed mainly of amorphous sodium silicate useful as a builder for detergent and having water-softening property and low hygroscopicity. CONSTITUTION: This amorphous sodium silicate-metal sulfate composite powder contains a metal sulfate such as sodium sulfate in the form of a solid solution and satisfies the formulas 1.6<=n<=2.8 and 0.1<=S<=2.0 wherein (n) is SiO2 /Na2 O molar ratio and S(m<2> /g) is the specific surface area of the powder. The powder can be produced by pulverizing a sodium silicate cullet containing a metal sulfate in the form of a solid solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous sodium silicate / metal sulfate composite powder having a water softening property and a small hygroscopicity and useful as a detergent builder, and a method for producing the same.

[0002]

Amorphous sodium silicate has been known for a long time. A typical example thereof is amorphous sodium silicate cullet (small piece of sodium silicate glass) obtained by heating and melting silica sand and sodium carbonate or sodium hydroxide.
The molar ratio n of iO ₂ / Na ₂ O is generally n = 2 to 3.3. The water glass solution in which amorphous sodium silicate cullet is dissolved in water under high pressure is the most versatile material in the manufacturing industry in all fields, but amorphous sodium silicate cullet itself is an intermediate product. There is no report of amorphous sodium silicate cullet which has strong color and is useful as a detergent builder.

The present inventors have found that a pulverized product of amorphous sodium silicate cullet exhibits water softening property and can be suitably used as a detergent builder and has already proposed it (Japanese Patent Application No. 6-161867).

The present inventors believe that when sodium silicate powder is dissolved in water, Na ions are first eluted, and then silicate ions are eluted. Further, it is considered that the water softening mechanism of the sodium silicate powder is due to the reduction of the concentration of Ca ion and Mg ion in water as follows.

Ca ion: Ca ion is bonded to silicic acid which remains without being dissolved even after Na ion is eluted.

Mg ion: The eluted silicate ion forms a precipitate of Mg ion and magnesium silicate.

By the way, for the Mg ions to decrease the concentration to generate OH ^over ion magnesium hydroxide precipitate in the solution, also Mg ion concentration in water is found to be much less than the Ca ion concentration There is. Therefore, the present inventors considered that in order to enhance the water softening performance, it is sufficient to prepare sodium silicate capable of binding a large amount of Ca ions. That is, it is sufficient to increase the elution of Na ions from sodium silicate, while suppressing the dissolution of silicate ions to increase the binding sites of Ca ions by silicic acid. It has been found that such sodium silicate can be prepared by controlling the SiO ₂ / Na ₂ O molar ratio n and the specific surface area of the sodium silicate.

However, when the SiO ₂ / Na ₂ O molar ratio n is decreased, the elution of Na ions is accelerated, and the initial water softening performance is increased, but the hygroscopicity is increased, and the moisture is absorbed during long-term storage. There was a problem that it changed into a water candy shape, and if so, the water softening property was lost.

[0009]

Therefore, an object of the present invention is to provide a powder mainly composed of amorphous sodium silicate which has a large water softening property and a small hygroscopicity and can be suitably used as a detergent builder, and a method for producing the same. To provide.

[0010]

The present inventors have been involved in the production of sodium silicate cullet for a long time, and have conducted extensive research on the production and physical properties of sodium silicate cullet. As a result, they have found that hygroscopicity can be reduced by solid-dissolving amorphous sodium silicate cullet with a metal sulfate, and the present invention has been proposed.

That is, the present invention contains the metal sulfate as a solid solution, the molar ratio of SiO ₂ / Na ₂ O is n, and the specific surface area is S (m ² / g). It is an amorphous sodium silicate / metal sulfate composite powder characterized by satisfying 1.6 ≦ n ≦ 2.8 0.1 ≦ S ≦ 2.0.

In the present invention, the metal sulfate is contained as a solid solution in the amorphous sodium silicate / metal sulfate composite powder (hereinafter simply referred to as composite powder). It is believed that the metal sulphate elutes first when the composite powder is added to water and increases the substantial contact area between the amorphous sodium silicate and water. Further, since the contact area with water increases, when the same water softening property is exhibited, SiO ₂ / N
It is believed that the molar ratio of a ₂ O can be increased and the Na ₂ O content can be decreased, resulting in a decrease in hygroscopicity.

Examples of the metal sulfates include alkali metal sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, and cesium sulfate; alkaline earth metal sulfates such as magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate; Aluminum sulfate or the like can be used. From the viewpoint of a blending component of a detergent, an alkali metal sulfate is preferable, and sodium sulfate is more preferable.

The amount of metal sulfate present can be quantified by analyzing elemental sulfur. For example, the sulfur element can be quantified by fluorescent X-rays described later. The elemental sulfur in the composite powder of the present invention is 0.3% by weight to
It is preferably in the range of 9.0% by weight in order to increase the contact area with water and to exhibit the water softening property satisfactorily. In order to exhibit a better water softening property, the sulfur element is preferably 0.7% by weight to 7.0% by weight,
It is more preferably 1.0% by weight to 4.0% by weight.

In the composite powder of the present invention, the metal sulfate is in solid solution. However, the metal sulphate that forms a solid solution has a solid solution limit, and its value depends on the type of metal sulphate and the molar ratio of amorphous sodium silicate. For example, when the metal sulfate is sodium sulfate, the solid solubility limit is about 15% by weight. Therefore, when the metal sulfates are contained in excess of the respective solid solution limit values, the metal sulfate phase that cannot be completely dissolved precipitates in the sodium silicate phase in which the metal sulfate is dissolved, resulting in a sea-island structure. To form. Furthermore, when the particles having such a sea-island structure are crushed, the metal sulfate phase and the sodium silicate phase in which the metal sulfate is solid-solved independently form particles, and a mixture of these particles is formed. To do. In the present invention, it is sufficient that the amorphous sodium silicate / metal sulfate composite particles in which a metal sulfate is dissolved are formed.
Therefore, the metal sulfate phase may be precipitated in the amorphous sodium silicate / metal sulfate composite particles in which the metal sulfate is solid-dissolved, or the amorphous sodium silicate / metal in which the metal sulfate is solid-dissolved. The sulfate composite particles and the metal sulfate particles may be mixed.

As described above, the water softening performance and hygroscopicity of the composite powder according to the present invention are determined by the molar ratio (Si
It is also affected by O ₂ / Na ₂ O). If the molar ratio of SiO ₂ / Na ₂ O is n, the following formula 1.6 ≦ n ≦ 2.8 must be satisfied. However, here the denominator of Na ₂ O
Is Na ₂ O based on sodium silicate and does not contain sodium based on metal sulfate. When n is smaller than 1.6, the hygroscopicity is increased and the dissolution of silicate ions in the composite powder is accelerated, and Ca ions that have once bound with silicic acid are eluted again into water, resulting in a water softening property. It becomes scarce and is not preferable. On the other hand, when n is larger than 2.8, the elution amount of Na ions is reduced and the number of sites binding with Ca ions is reduced, resulting in poor water softening property, which is not preferable. In order to exhibit more favorable water softening property and suppress hygroscopicity, it is preferable that 1.8 ≦ n ≦ 2.2 is satisfied.

Further, the water softening performance and hygroscopicity of the composite powder of the present invention are affected by its specific surface area. When the specific surface area of the composite powder is S (m ² / g), the following formula 0.1 ≦ S ≦ 2.0 must be satisfied. Specific surface area is 0.1m ²
If it is less than / g, the elution amount of Na decreases and the water softening performance decreases, which is not preferable. On the other hand, when the value of the specific surface area is more than 2.0 m ² / g, the dissolution of silicate ions is accelerated at the same time as the elution of Na, the water softening property is deteriorated and the hygroscopicity is the same as when the molar ratio n is low. Also increases, which is not preferable. The specific surface area is 2.0 m ² / g
Making it larger is very difficult with common grinding methods. In order to exhibit more favorable water softening property and suppress hygroscopicity, 0.5 ≦ S ≦ 1.5 is preferable.

The composite powder of the present invention is amorphous. However, this includes not only the case of being completely amorphous, but also the case of containing fine crystals of sodium silicate and fine crystals of metal sulfate. In general, in an X-ray diffraction pattern of an amorphous substance containing fine crystals, a broad peak is recognized in a halo pattern due to the amorphous substance. This broad peak is due to fine crystals contained in the amorphous material. The amount of fine crystals can be determined from the area of broad peaks in the halo pattern.

The term "amorphous" in the present invention includes the case where fine crystals are contained in the amorphous. In order to be amorphous, generally, the amount of fine crystals obtained from the area of broad peaks in the halo pattern is 20% by volume.
It is preferably less than.

The average particle size of the composite powder of the present invention is preferably in the range of 1 to 100 μm, as measured by a liquid phase spontaneous sedimentation particle size distribution meter.

The composite powder of the present invention may be manufactured by any method, but it is preferable to manufacture it by the following method because it is a simple process. That is, it is a method of crushing sodium silicate composite cullet containing a metal sulfate as a solid solution.

The sodium silicate composite cullet can be manufactured by the following method. For example, metal sulfate and SiO ₂ and sodium carbonate or sodium hydroxide are added to the SiO ₂ / Na ₂ O of the sodium silicate composite cullet.
Is melted by heating so that the molar ratio n becomes 1.6 ≦ n ≦ 2.8, and then cooled.

As the metal sulfate, the above-mentioned compounds can be used. The metal sulfate may be anhydrous or hydrated salt. As SiO ₂ , Si such as silica stone, silica sand, cristobalite stone, fused silica, amorphous silica, silica sol, etc.
A known substance containing O ₂ as a main component can be used without any limitation. Industrially, silica sand is preferably used because it is inexpensive and easy to handle. Furthermore, sodium carbonate or sodium hydroxide, which is an alkali source, may be used alone, or may be used by mixing them at an arbitrary ratio.

These raw materials are heated and melted. The temperature at that time must be in the range of 900 to 1300 ° C.
When the heating and melting temperature is lower than 900 ° C., SiO ₂ is not melted and the intended sodium silicate composite cullet is not formed, which is not preferable. On the other hand, if it exceeds 1300 ° C, the metal sulfate is decomposed, the solid solution amount of the metal sulfate decreases, and the hygroscopicity suppressing effect decreases, which is not preferable. Furthermore, the preferable heating and melting temperature is 1000 to 1200 ° C.

A shorter heating and melting time is economically preferable, and a sufficiently uniform melt is produced in 10 hours or less. The method for cooling the melt may be such that the sodium silicate phase in which the produced metal sulfate is solid-solved becomes amorphous. Generally, cooling to such an extent that the molten state is taken out to the room temperature environment is sufficient. As a cooling method, a method of gradually cooling in a furnace or water cooling can be adopted in addition to a method of simply cooling by air.

The sodium silicate composite cullet obtained by cooling is then ground. For the pulverization, a known pulverization method can be adopted. For example, a fine mill such as a ball mill, a stirring mill, a high-speed rotary fine mill, a jet mill, a shear mill and a colloid mill can be used. Among these, a ball mill can be mentioned as the most common crusher. Specific examples thereof include rolling mills such as pot mills, tube mills and conical mills; circular vibration mills,
Vibratory ball mills such as rotary vibration mills and centrifugal mills; and planetary mills.

In order to increase the efficiency of pulverization by the above-mentioned fine pulverizer, before the fine pulverization operation, a medium crusher such as a jaw crusher, a gyratory crusher, a cone crusher, a hammer crusher, or a coarse crusher is used to adjust the crushing to about several mm. It is preferable to crush it into grains.

Further, a grinding aid can be used in order to increase the grinding efficiency. As a grinding aid, "Latest powder material design (published by Techno System Co., Ltd.)"
Known grinding aids such as those listed in Table 2.5 can be used without any restrictions. Diethylene glycol and triethanolamine are preferable from the viewpoint of compatibility with sodium silicate composite cullet. The addition amount of the grinding aid is 1% by weight or less.

[0029]

EFFECT OF THE INVENTION The composite powder obtained by the present invention exhibits excellent water softening ability, and also has excellent storage stability due to its low hygroscopicity.

[0030]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The measured values in Examples and Comparative Examples were measured by the following methods.

(1) Quantification of sulfur element p in the composite powder The concentration (% by weight) of the sulfur element in the composite powder was measured by a fluorescent X-ray analyzer.

(2) Molar ratio n of composite powder The composite powder was dissolved in water, the amount of sodium oxide and the amount of silica in the solution were individually measured, and the molar ratio n was calculated from the ratio.

Amount of sodium oxide A methyl orange solution was used as an indicator and neutralization titration was carried out with a hydrochloric acid solution.

Amount of silica Sodium fluoride was reacted with the sample, and the liberated sodium hydroxide was neutralized and titrated with hydrochloric acid. The amount of silica was determined by subtracting the amount corresponding to sodium oxide from the required amount of hydrochloric acid.

H ₂ SiO ₃ + 6NaF + H ₂ O → Na ₂ Si
F ₆ +4 NaOH (4 mol of sodium hydroxide is precipitated per 1 mol of silica.) (3) Specific surface area of composite powder It was measured using a permeation method (constant pressure air permeation method). Specifically, the specific surface area Sw was obtained by measuring the mass W and the time t from the following Kozeny-Carman equation.

Sw = (140 / ρ) × ((ΔP × A × t) / (η × L ×
Q) × ε ³ / (1-ε) ² ) ^1/2 where ε is the porosity of the sample packed layer, ε = 1-W / (ρ × A × L) ρ: Powder density g / cm ³ η: Viscosity coefficient of air mPa sec L: Sample layer thickness cm Q: Sample layer permeation air volume cm ³ △ p: Pressure difference between both ends of sample layer g / cm ² A: Cross sectional area of sample layer cm ² t: Time required for Qcm ³ air to pass through the sample layer
sec W: It is the weight g of the sample. Here, L = 1.2 cm, Q = 20 cm ³ , ΔP =
30 g / cm ² , A = 2 cm ² , ρ is the true specific gravity of the cullet before crushing, and η is 1a from the Chemical Handbook (Revised 3rd Edition Basic Edition II).
0.0182 mPa sec which is the value of tm and 25 ° C was adopted.

(4) Amount of fine crystals When an X-ray diffraction pattern of the composite powder shows a broad peak near 2θ = 32 ° as shown in FIG. 1, the amount of fine crystals should be determined from the area of the broad peak. You can This broad peak is bent from the halo pattern around 2θ = 26 ° and around 2θ = 36 °.
Conclusion These two bending points in a straight line was calculated integrated intensity of the broad peak that straight as a background (this value and NI _B). On the other hand, the integrated intensity of all patterns is
A point when the point of time of 2 [Theta] = 8 ° and 2 [Theta] = 125 [deg connected by a straight line, and calculates the linear as a background (this value and NI _T). The amount of fine crystals was calculated using the above values.

Amount of microcrystals (volume%) = (NI _B / NI _T ) × 100 (5) Water softening ability (Ca sequestering ability) The water softening ability of the composite powder is represented by the Ca sequestering ability. 5mm adjusted to pH = 10 with ethanolamine and hydrochloric acid
1 L of an ol / L calcium chloride aqueous solution was kept at 20 ° C. while stirring at 350 rpm. Next, 0.2 g of the composite powder as a sample was precisely weighed (unit: g) and added to the above solution. After stirring at 350 rpm for 15 minutes, 10 ml was sampled and filtered through a 0.2 μm filter.
The Ca concentration in the obtained filtrate was measured by an inductively coupled plasma emission spectrophotometer (ICP-AES), and the Ca ion amount C (unit: mg) was calculated from this value. The Ca blocking ability was evaluated by the value calculated by the following formula.

Ca blocking ability = (20-C) /0.2
(Unit: mg / g of sample) (6) Hygroscopicity Approximately 20 g of sample was put into a resin cup and left for 3 days in a constant temperature and humidity chamber at a temperature of 25 ° C and a humidity of 50%.
W was measured, and the moisture absorption amount (% by weight) was calculated from the ratio with the initial weight W ₀ by the following formula.

Moisture absorption amount = (ΔW / W ₀ ) × 100
(Unit: wt%) Example 1 200 g of silica sand (SiO ₂ 99.8%), 176.4 g of sodium carbonate (Na ₂ CO ₃ 99%) and 59.1 g of anhydrous sodium sulfate were mixed, and 100 g of water was added, Further mixed. The mixture was put into a platinum crucible, heated from room temperature to 1200 ° C in 1.5 hours in an electric furnace, and then kept at 1200 ° C for 3 hours. After heating and melting, the crucible containing the contents of the cauterizing state was taken out of the electric furnace, immersed in a water bath and rapidly cooled to obtain a cloudy sodium silicate composite cullet. The obtained sodium silicate composite cullet was crushed with a jaw crusher (gap 5 mm). Then, ball mill (pot; inner diameter 135mm, capacity 2
L, balls; diameter 30 mm × 33 pieces, made of Al ₂ O ₃ ) and crushed at a rotation speed of 60 rpm for 1 hour. Then, add 0.5% by weight of the composite powder of diethylene glycol,
Further, it was pulverized under the same conditions for 65 hours.

The SiO ₂ / Na ₂ O molar ratio n of the obtained composite powder was 2.00, and the content of elemental sulfur based on sodium sulfate was 3.7% by weight. When the crystallinity of the composite powder was evaluated by X-ray diffraction, it showed a halo pattern as shown in FIG. Broad peaks were observed near 2θ = 32 °, and the amount of fine crystals obtained from the area of the broad peaks in the halo pattern was 9% by volume. The physical properties of the composite powder are summarized in Table 1.

Example 2 A colorless and transparent sodium silicate composite cullet was obtained in the same manner as in Example 1 except that the amount of anhydrous sodium sulfate added was 26.3 g. This was crushed in the same manner as in Example 1 to obtain a composite powder, and the results are shown in Table 1.

Example 3 A cloudy sodium silicate composite cullet was obtained in the same manner as in Example 1 except that the heating and melting temperature was 1100 ° C., and this was pulverized in the same manner as in Example 1 to obtain a composite powder. The results are summarized in Table 1.

Example 4 A cloudy sodium silicate composite cullet was obtained in the same manner as in Example 1 except that the amounts of silica sand, sodium carbonate and anhydrous sodium sulfate were 200 g, 196 g and 60 g, respectively. This was crushed in the same manner as in Example 1 except that the crushing time was 140 hours to obtain a composite powder. The physical properties of the composite powder are summarized in Table 1.

Example 5 A colorless and transparent sodium silicate composite cullet was obtained in the same manner as in Example 1 except that the amounts of silica sand, sodium carbonate and anhydrous sodium sulfate were 200 g, 168 g and 25 g, respectively. It was crushed in the same manner as above to obtain a composite powder. The results are summarized in Table 1.

Comparative Example 1 Silica sand and sodium carbonate were mixed in an amount of 187.5, respectively.
g, 212.5 g, and colorless and transparent sodium silicate cullet was obtained in the same manner as in Example 1 except that anhydrous sodium sulfate was not used. This was pulverized in the same manner as in Example 1 to obtain amorphous sodium silicate powder. The results are summarized in Table 1.

Comparative Example 2 Silica sand and sodium carbonate were mixed in amounts of 177 g and 2 respectively.
A colorless and transparent sodium silicate cullet was obtained in the same manner as in Example 1 except that the amount was 33 g and anhydrous sodium sulfate was not used. This was pulverized in the same manner as in Example 1 to obtain amorphous sodium silicate powder. The results are summarized in Table 1.

[0048]

[Table 1]

[Brief description of drawings]

FIG. 1 is an X-ray diffraction pattern of the amorphous sodium silicate / metal sulfate composite powder of the present invention obtained in Example 1.

[Procedure amendment]

[Submission date] March 1, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

Comparative Example 1 Silica sand and sodium carbonate were mixed at 212.5 , respectively.
g, 187.5 g, and colorless and transparent sodium silicate cullet was obtained in the same manner as in Example 1 except that anhydrous sodium sulfate was not used. This was pulverized in the same manner as in Example 1 to obtain amorphous sodium silicate powder. The results are summarized in Table 1.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

Comparative Example 2 Silica sand and sodium carbonate were mixed in amounts of 177 g and 2 respectively.
A colorless and transparent sodium silicate cullet was obtained in the same manner as in Example 1 except that the amount was 23 g and anhydrous sodium sulfate was not used. This was pulverized in the same manner as in Example 1 to obtain amorphous sodium silicate powder. The results are summarized in Table 1.

Claims (2)

[Claims] 1. A solid solution containing a metal sulfate, and SiO.
_When the molar ratio of ₂ / Na ₂ O is n, the specific surface area is S (m ² /
g), an amorphous sodium silicate / metal sulfate composite powder characterized by satisfying the following formula: 1.6 ≦ n ≦ 2.8 0.1 ≦ S ≦ 2.0. 2. The method for producing an amorphous sodium silicate / metal sulfate composite powder according to claim 1, wherein sodium silicate cullet containing a solid solution of metal sulfate is pulverized.